The present invention relates to a device for transmitting yarn monitoring signals to the control circuit of a spinning station of an open-end spinning machine for determining actuation and deactuation of a sliver feeding device.
In open-end spinning machines, a yarn monitor determines whether a yarn spun by the spinning station is drawn off or whether the travel path of the yarn has been interrupted. If the yarn monitor determines that the spinning of the yarn has stopped, then the feeding of sliver at the spinning station is interrupted. However, problems in the circuit of a yarn monitor can cause the feeding device for the sliver to continue operation although a yarn break has occurred. Such an error can remain unnoticed for a rather long time if the sliver is removed via the suction conduit connected to the spinning chamber due to the prevailing spinning vacuum applied. However, there is also the possibility that the fibers collect in the spinning chamber and clog it. There is the further danger, especially in high-speed rotor spinning machines, that the fibers become heated and ultimately burn on account of the frictional heat.
German Patent Publication DE-OS 25 43 324 teaches an electric circuit arrangement for a yarn-break detecting element for textile machines, especially for fine spinning machines without spindles. A mechanical yarn feeler is utilized as a yarn-break detecting element. The attempt has already been made with the circuit disclosed in this publication to reduce the susceptibility to trouble of the control circuit, especially as concerns the possible failure of a transistor. The circuit therefore does not contain any transistors. However, the circuit is nevertheless not trouble-free since the contacts can remain stuck in the switch which is magnetically actuated upon a yarn break, as a result of which a signal flow indicating the presence of the traveling yarn path nevertheless remains preserved.
In electronic yarn monitors, a yarn traveling in a measuring slot of the yarn monitor generates a yarn traveling signal as the output of the sensor monitoring the yarn. This yarn traveling signal is transformed via switching amplifiers and fed as a direct-current signal to the control circuit of the spinning station. Upon failure of the yarn traveling signal, the drawing-in of the sliver is stopped.
FIG. 1 shows a simplified view of a block circuit diagram of the circuit of an electronic yarn monitor, explained in detail further below, as currently used in textile machines. A defect in an electronic component in the circuit of the yarn monitor or in the receiver itself, produced for example by an error in the voltage supply of the yarn monitor or by the sudden discharge of static electricity produced by the running yarn in the measuring slot, can cause the control circuit to fail to receive a yarn traveling signal at the spinning station or to constantly receive a yarn run signal even though no yarn is being spun any more, which is considerably more dangerous in its effect. If, for example, a short circuit between an emitter and a collector, i.e., a so-called transalloying, arises in the circuit transistor for the yarn traveling signal, the transistor can no longer be switched. The voltage signal then constantly assumes the value indicating continued traveling of the yarn, as a result of which fibers continue to be fed to the spinning station with the consequences indicated. Therefore, it must be absolutely assured that the infeed of fibers into the spinning chamber ceases if the yarn travel path is interrupted.